From 49646e1dc30d7a49944631f7d3f7738f24c6893f Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Mon, 17 Oct 2022 18:00:53 +0200
Subject: [PATCH] sys/event: add event sources

This adds an event bus where multiple events can be triggered at once.
---
 sys/include/event/source.h | 118 +++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 sys/include/event/source.h

diff --git a/sys/include/event/source.h b/sys/include/event/source.h
new file mode 100644
index 0000000000..8e6f5a2e32
--- /dev/null
+++ b/sys/include/event/source.h
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2022 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     sys_event
+ * @brief       Provides functionality to trigger multiple events at once
+ *
+ * @{
+ *
+ * @file
+ * @brief       Event Source API
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ *
+ */
+
+#ifndef EVENT_SOURCE_H
+#define EVENT_SOURCE_H
+
+#include "event.h"
+#include "list.h"
+#include "irq.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Event source struct
+ */
+typedef struct {
+    list_node_t list;       /**< event source list node */
+} event_source_t;
+
+/**
+ * @brief   Subscriber of an event source
+ */
+typedef struct {
+    list_node_t node;       /**< event subscriber list node  */
+    event_t *event;         /**< pointer to event that should be triggered */
+    event_queue_t *queue;   /**< event queue to be used for the event */
+} event_source_subscriber_t;
+
+/**
+ * @brief   Initialize an event source
+ */
+#define EVENT_SOURCE_INIT  { 0 }
+
+/**
+ * @brief   Initialize an event source subscriber
+ *
+ * @param[in]   e       The event to trigger
+ * @param[in]   q       The event queue to use for the event
+ */
+#define EVENT_SOURCE_SUBSCRIBER_INIT(e, q) { .event = (event_t *)e, .queue = q }
+
+/**
+ * @brief   Attach an event to an event source
+ *
+ * @param[in]   source  The event list to attach the event to
+ * @param[in]   event   The new event subscription
+ */
+static inline void event_source_attach(event_source_t *source,
+                                       event_source_subscriber_t *event)
+{
+    unsigned state = irq_disable();
+
+    list_add(&source->list, &event->node);
+
+    irq_restore(state);
+}
+
+/**
+ * @brief   Remove a subscription from the event source
+ *
+ * @param[in]   source  The event list to remove the event from
+ * @param[in]   event   The event to remove
+ */
+static inline void event_source_detach(event_source_t *source,
+                                       event_source_subscriber_t *event)
+{
+    unsigned state = irq_disable();
+
+    list_remove(&source->list, &event->node);
+
+    irq_restore(state);
+}
+
+/**
+ * @brief   Trigger all events registered on the event source
+ *
+ * @param[in]   source  The event list to trigger
+ */
+static inline void event_source_trigger(event_source_t *source)
+{
+    unsigned state = irq_disable();
+
+    event_source_subscriber_t *event = container_of(source->list.next,
+                                                    event_source_subscriber_t,
+                                                    node);
+    while (event) {
+        event_post(event->queue, event->event);
+        event = container_of(event->node.next, event_source_subscriber_t, node);
+    }
+
+    irq_restore(state);
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* EVENT_SOURCE_H */
+/** @} */